Physicochemical characterization of amino functionalized synthetic clay/Nafion nanocomposite film with embedded platinum nanoparticles for PEM fuel cells

A novel aminopropyl functional group bearing magnesium phyllosilicate clay (AC)/Nafion nanocomposite films with embedded platinum nanoparticles (Pt/AC/N) was prepared by sol–gel method followed by solution casting for various compositions of AC in Nafion. The as prepared nanocomposite films were subjected to surface characterization by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The thermal and mechanical stabilities were analyzed by thermogravimetric analysis (TGA) and nanoindentation coupled scanning probe microscopy analysis (SPM). The protonic conductivity of AC/Nafion nanocomposite films with and without Pt nanoparticles was measured by electrochemical impedance spectroscopy (EIS) using a two-probe conductivity cell. It was found that 6 wt.% AC/Nafion possesses a high proton conductivity of 1.38 × 10− 4 S cm− 1, a thermal stability of up to 360 °C (60 °C higher than pristine Nafion) and a high mechanical stability (78.76 MPa) among the different compositions studied. The catalytic activity of the optimized nanocomposite film containing Pt nanoparticles (Pt/6 wt.% AC/N) towards oxygen reduction reaction (ORR) was investigated by cyclic voltammetry (CV) and linear scan voltammetry (LSV) techniques under hydrodynamic conditions. It was observed that 35.4 μg cm− 2 Pt/6 wt.% AC/N composite film has higher ORR limiting current density of 4.2 mA cm− 2, and also it is interesting to note that this composition exhibited a high conductivity of 1.75 × 10− 3 S cm− 1 indicating that the nanocomposite catalyst film could be used as a proton conductor as well as a catalyst layer for the fabrication of membrane electrode assemblies in PEM fuel cells.